The propagation and attenuation of lightning electromagnetic field through stratified soil are studied with the Wait and Cooray approximate methods, considering different conductivities in the upper and lower soil layers. The simulation results are examined by the FDTD method. Under the condition of larger soil conductivity in the upper layer than the lower layer, both approximate methods can acquire good simulation accuracy. While under the condition of a smaller soil conductivity in the upper layer than the lower layer, some errors are involved in the Cooray approximation, and the result of Wait approximation with good accuracy reasonably represent the interference effect which leads to elective enhancement of lightning electromagnetic field in high frequency, and consequently, with the attenuation factor being larger than 1 and oscillation occurred.